There are a number of diseases or disorders of the eye and/or the optic nerve thereof, including central retinal vein occulsion (CRVO). CRVO is a difficult and often frustrating disease for both the ophthalmologist and the patient. Even in non-ischemic presentations, the majority of patients are left with poor vision, and in those patients with wide-spread capillary non-perfusion (essentially a no-blood flow type of condition), less than 10% of patient's have better than 20/400 vision. Stated another way, CRVO leads to the degradation of the condition of the eye which could ultimately lead to a loss of vision in the afflicted eye. No treatment has been proven to be useful in improving the vision of an eye exhibiting CRVO. The ophthalmologist is usually left to follow the patient, after ensuring adequate systemic work-up, and watch for the development of iris neovascularization.
Neovascularization is the term used to describe the process whereby new blood vessels are formed in the cornea in response to anoxia, the absence of oxygen. Although this might seem beneficial, the formation of such new blood vessels usually results in further degradation of the vision in the affected eye because of the blockage of light and/or the creation of retinal detachments. In any event, and as described below, the CRVO usually occurs in a central retinal vein and thus the formation of additional capillaries or blood vessels do not increase the level of available oxygen to the eye.
As shown in FIG. 1, the sclera of a human eye 2, what is commonly referred to as the white area of the eye, composes about ⅚ of the outside surface of the eye globe. The sclera goes from the limbus in the front or anterior of the globe, which is the junction between the white of the eye and the colored or iris of the eye to the optic nerve located at the posterior of the globe. The sclera is very strong, opaque and inelastic and generally is for maintaining the form and shape of the eye globe and to keep stray light from entering the eye. The sclera varies in thickness and has many blood vessels and nerves passing through it. The area where the optic nerve passes through the sclera is a sieve-like structure called the lamina cribosa.
Histological studies suggest that regardless of the level of perfusion, most or all CRVO's occur from thrombus formation in the central retinal vein at the level of the lamina cribosa. With the relatively denser connective tissue that makes up the lamina cribosa encircling the retinal blood vessels, it is at this level that the luminal diameter of the central retinal vein is the narrowest. Anatomically, thus it is at this level that a literal bottle-neck exists. The resultant increased turbulence in blood flow, and possible increased endothelial cell damage, makes this a theoretically higher risk area for thrombus formation to occur.
It thus would be desirable to provide a new device that can release the constrictive pressure on the central retinal vein by the dense connective tissue encircling or surrounding the central retinal vein and thereby increase the luminal diameter of the central retinal vein in the lumina cribosa, as well as providing new methods to treat a CRVO afflicted eye. It would be particularly desirable to provide such a device and method that can effect such a release in constrictivity with minimal risk to violating the structural integrity of the central retinal vein as well as minimizing the collateral damage to optical nerve fibers. Such collection devices preferably would be simple in construction and such methods are easily adaptable and integratable with existing retinal surgical procedures and techniques.